The most common and most likely answer to this crossword clue is the 8 letter word EPILOGUE
I've seen this crossword clue in The Daily Telegraph
E
P
I
L
O
G
U
E
More clues leading to the result EPILOGUE
- Oriental canoe changes hands, that’s the last you hear
- In conclusion, town’s first Republican leaving elite group unsettled
- Final section from record, one left by villain, not right
- In final speech, low-class cheek’s conjured up by rascal, right to be rejected
- Final chapter Poe composed with guile
- Rat runs out beyond rubbish pile in end passage
- Originally Elvis Presley single record heard last thing on air
- The last thing you’d expect an actor to say?
- Ending record, single record by Posh Spice finally
- One breaking record after record, often rules at close of play
Buddy explains!

The straight part
We know that "The last thing you’d expect an actor to say" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the last thing you’d expect an actor to say = epilogue.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does EPILOGUE mean?
EPILOGUE noun- A short speech, spoken directly at the audience at the end of a play
- The performer who gives this speech
- A brief oration or script at the end of a literary piece; an afterword
- A component of a computer program that prepares the computer to return from a routine.
- To conclude with an epilogue.